Arthroscopic surgical procedures have vastly improved the ability of orthopedic surgeons to treat injuries to joints. An example of one such procedure is the replacement of anterior cruciate ligaments (ACL) of the knee. Torn or ruptured ligaments which may be caused by "sport injuries" (so referred to due to the frequency of knee injuries in sports such as football or skiing) may now be replaced by tendon grafts or artificial ligaments.
One of the problems involved in replacing ligaments, and particularly the ACL, is the need to provide a firm permanent fixation point for the replacement graft. It is important that the device or system for securing the graft be relatively easy to install with the aid of endoscopic techniques. An important feature of devices for fixing grafts to bones also includes the ability to adjust the device, if necessary, after installation. Similarly, the ability to initially control the depth of insertion of the fixation device is an important consideration.
With any fixation device or system for securing a ligament graft to a bone or bone-like structure, it is important not to damage the graft during installation. It is another objective of anchoring systems to minimize trauma. One way to minimize trauma is to limit the number and size of the access openings to the joint required for completion of the graft operation. By minimizing the number of openings, the time required for the procedure and for post operative recuperation is minimized.
In the past, ligament grafts were usually secured to bones by staples or screws. These types of devices are simple and effective, but typically require access to both ends of the ligament graft and also require longer lengths of graft tendons or artificial ligaments. These problems led to the development of other ligament anchor systems, such as that disclosed in U.S. Pat. No. 4,772,286. That patent discloses a ligament attachment method and apparatus having an artificial cruciate ligament with tensionable cone elements on one or both ends. Another embodiment disclosed in that patent discloses a process and device in which a rolled replacement tendon is sutured to a threaded cylinder which is installed with a hex driver.
Other known devices are disclosed in U.S. Pat. No. 4,870,957. That patent discloses a ligament anchor in which a two part device is provided on each end of the ligament. This device allows for a single entry point for placement of the ligament, but requires that a special spring clip be inserted into a previously secured threaded footing. A clip having a flared end is snapped into the installed footing. The clips are maneuvered with the tendon attached through holes in the femur and tibia in which the anchors have been previously set.
The devices and procedures discussed above are fairly time consuming and complicated to use and, if not carefully performed, could result in damage to the graft.
These and other problems are addressed by the present invention.